Collection of sulfur values from flue gasses generated by metallic sulfide smelting and converting

ABSTRACT

In the processing of nonferrous sulfide ores, the resulting flue gas, which contains sulfur dioxide, is passed through an aqueous scrubber containing calcium sulfate or calcium sulfite. The resulting SO2 collection is several times greater than in the case of prior scrubbing techniques. This system also has application in scrubbing flue gas from sulfur bearing fuel.

United States Patent 1191 McKie Nov. 27, 1973 [75] Inventor: Robert T.McKie, Marenisco, Mich.

[73] Assignee: Copper Range Company, New

York, NY.

22 Filed: Mar. 19, 1971 21 Appl. No.: 126,368

Related US. Application Data [63] Continuation of Ser. No. 748,090, July26, 1968,

2,080,779 /1937 Lessing 23/2 SQ 2,453,775 11/1948 Beath et 81.... 23/178R 3,386,798 6/1968 Bevans et a1... 23/178 R 3,477,815 11/1969 Miller eta1. 23/178 R 2,233,841 3/1941 Lepsoe 23/178 2,351,780 6/1944 Palmrose23/178 2,696,424 12/1954 Schoeffel... 23/178 3,281,236 /1966 Meissner75/74 Primary Examiner-Oscar R. Vertiz Assistant Examiner-1-loke S.Miller Attorney-Gerald Altman abandoned. [57 ABSTRACT 52 us. c1 75/74,423/242, 423/541 In the Processing of nonferrous Sulfide ms, the result-511 1111.01. c221) /04, COlb 17/50 s flue gas, which contains sulfurdioxide. is passed 58 Field of Search 23/2 so, 178; through an aqueousScrubber containing Calcium 423/541, 7 fate or calcium sulfite. Theresulting SO, collection is several times greater than in the case ofprior scrub- 5 References Cited bing techniques. This system also hasapplication in UNITED STATES PATENTS scrubbing flue gas fromsulfurbearing fuel. 2,073,039 3/1937 Wilton et al. 23 2 so 1 Claim, 1Drawing Figure TO ATMOSPHER Efi FLUE GASES 3 s0 WET -1 5 SCRUBBER 2 2008 +00 0 DE- HEAT 82 6 GASER IN C 0 80 SLURRY To HEAT H SCRUBBEREXCHANGER SPRAYS PATENTEDNUVZT I975 FLUE GASES a $0 ATMOS PH SCRUBBERSPRAYS INVENTOR ATTORNEYS COLLECTION OF SULFUR VALUES FROM FLUE GASSESGENERATED BY METALLIC SULFIDE SMELTING AND CONVERTING RELATEDAPPLICATION The present application is a continuation of U.S. Pat.application Ser. No. 748,090, July 26, 1968, now abandoned.

BACKGROUND AND SUMMARY The present invention relates to the processingof nonferrous sulfide ores, whereby first an ore or ore concentrate issmelted to a metallic matte and an initial barren slag, and thenmetallic matte is converted into the contained nonferrous metal, sulfurdioxide and augmented barren slag. In the foregoing process, the heatfor smelting is generated by burning a carbonaceous fuel within thesmelting furnace, with the result that the flue gas leaving the furnacecontains the aforementioned sulfur dioxide. The sulfur dioxideconstitutes both a pollutant and an undesired loss of sulfur whenpermitted to escape into the atmosphere. i

SUMMARY OF THE INVENTION The primary object of the present invention isto provide a superior sulfur dioxide trapping process involving passinga flue gas of the above type through an aqueous dispersion of calciumsulfate or calcium sulfite in order to form calcium compound of oxygenand sulfur, and heating the calcium compound of oxygen and sulfur afterisolation in order to release the sulfur dioxide as desired. It has beenfound that the collection efficiency of calcium sulfate or calciumsulfite is much higher than prior analogous materials and that a highyield of sulfur dioxide from calcium compound of oxygen and sulfur canbe achieved readily.

Other objects of thepresent invention will in part be obvious and willin part appear hereinafter.

The invention accordingly comprises the process characterized by thesteps, conditions, concentrations and relationships, which areexemplified by the following detailed disclosure, the scope of whichwill be indi cated in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of thepresent invention, reference is to be had to the accompanying drawingwherein:

The drawing is a flow diagram of an illustrative process of the presentinvention.

DETAILED DESCRIPTION Referring to the drawing, in accordance with thepresent invention, a nonferrous ore, i.e., an ore of copper, nickel,cobalt or lead, after being concentrated, is supplied as a charge to areverberatory furnace which is heated by burners 11. In reverberatoryfurnace 10, smelting occurs under conditions such that the metal oxidereacts with an iron or other sulfide (originally present or added as aflux) to form the metal sulfide and an iron or other oxide. The metalsulfide constitutes a matte. The heat for the furnace, which isgenerated by burning a carbonaceous fuel at 11, results in the formationof a large quantity of flue gas containing both metal bearing dust andsulfur dioxide, as well as the final combustion gases. Fromreverberatory furnace 10, the flue gas passes through a heat exchangerCaSO, S0 CaS O The resulting solution and slurry of calcium sulfate,calcium compound of oxygen and sulfur and water is fed to a de-gaser 16,in which heating occurs to a temperature ranging from 150 to 210F. Inconsequence, separation of SO gas occurs as follows:

CaS O Heat CaSO S0 The resulting solution and slurry of calcium sulfateis cooled by a heat exchanger 18 to a temperature ranging from 50 to100F. and recirculated through wet scrubber 14 for repetition of cycle.

In the foregoing process, the concentration of calcium sulfate orcalcium sulfite in water is not critical, the only requirement being astoichiometric excess with respect to the sulfur dioxide beingcollected. Good results are achieved with a fairly thick slurry ofbetween 5 and 15 percent by total weight of calcium sulfate and/orcalcium sulfite in water. With respect to the fluid passing into thede-gaser, any concentration of sulfur dioxide in excess of 10 grams perliter or 26 grams per liter of calcium compound of oxygen and sulfurwill result in good recovery per pass. The calcium sulfate or calciumsulfite normally is the sole active material in the slurry. However, insome applications, calcium hydroxide or limestone is added to increasethe calcium sulfite in accordance with the following reactions.

Ca(Ol-I) (I-Iydroxide) SO, CaSO H O CaCO (Lime) SO CaSO CO In accordancewith the present invention, a typical process involving the generationof sulfur dioxide involves copper production. A copper ore concentrate(following flotation of such an ore as chalcocite Cu S, covellite-CuS,chalcopyrite CuFeS bornite Cu FeS and enargite Cu (As Sb)S and roastingto lower the sulfur content) is charged into a reverberatory furnace andmelted at a temperature of approximately 2,400F. In reverberatoryfurnace 10, smelting occurs under conditions such that copper oxidereacts with iron sulfide (originally present or added as a flux) to formcopper sulfide and iron oxide, the copper sulfide forms copper matte,some of the contained sulfur is oxidized to sulfur dioxide, and gassesleaving the furnace include a smoke and sulfur dioxide The sulfurdioxide is captured by wet scrubber 14.

EXAMPLE In an experimental demonstration of the sulfur dioxidecollection process of the present invention, 1 liter of slurry wasprepared from 200 grams of 200 to 325 mesh CaSO, powder and water. Thisslurry was gassed with S0 until 84 grams of sulfur dioxide was absorbed.The slurry was allowed to settle and the clear solution then was heated.At F, S0 began to bubble out of solution, when the temperature reached184F, all the dissolved SO was removed. As the S evolved from thesolution, a copious feathery precipitate of CaSO, was formed.

The present invention thus provides an improvement in efficiency byutilizing gaseous effluents economically in order to save sulfur dioxideas a useful byproduct. Since certain changes may be made in theforegoing disclosure without departing from the present invention, it isintended that all matter described in the foregoing specification orshown in the accompanying drawing be interpreted in an illustrative andnot in a limiting sense.

What is claimed is:

1. In a copper ore smelting process by which ore is smelted to metallicmatte and initial barren slag and metallic matte is converted intocontained copper, sulfur dioxide and augmented barren slag, the sulfurdioxide constituting part of a flue gas, the steps of passing said fluegas through a scrubber presenting means against which an aqueousscrubbing fluid is sprayed and in contiguity with which said flue gas isflowed, said aqueous scrubbing fluid including an aqueous solution andslurry of at least one reactant member of the class consisting ofcalcium sulfate and calcium sulfite said reactant member being instoichiometric excess with respect to said sulfur dioxide, thetemperature of said scrubbirg fluid ranging between 50 and F., saidreactant member and said sulfur dioxide reacting to form a reactionproduct soluble in said scrubbing fluid, flowing said scrubbing fluidfrom said scrubber to a degaser, heating said scrubbing fluid in saidde-gaser to a temperature ranging from to 210F. in order to removesulfur dioxide therefrom, flowing said scrubbing fluid from saidde-gaser and cooling said scrubbing fluid, and returning said scrubbingfluid to said scrubber, whereby continuous cycling of said scrubbingfluid and removal of sulfur dioxide from said flue gas occurs, saidreactant member ranging between 5 and 15 percent by total weight of saidscrubbing fluid, said scrubbing fluid flowing from said scrubbercontaining,by total weight, said reaction product in a concentration ofat least 2 6 gramsper liter, said at least one reactant member being thesole active material in said slurry and being in stoichiometric excesswith respect to said sulfur dioxide, said cooling reducing thetemperature of said slurry to from 50 to 100F.

